Looks like crabgrass. Your coming up on the time of year to seed cool season grasses ( Tall fescue, bluegrass, ryegrass etc) I would think mid Sept. would be the right time to seed for your climate zone. The crabgrass goes brown in cold weather , and returns in May or so. Maybe hire a lawn service to dethatch (scalp the area), to insure your new seed will have good contact with the soil. Next spring (mid April) use a weed preventer (Dimension' is a good one) to prevent the crabgrass from coming back.

Thanks Tom! My guess is the lawn could use some nutrients as well. Should I put something down before or after seeding? If so, what would you recommend?

Crabgrass will die completely with the first frost. It only returns in the spring from seed. There are two requirement for crabgrass to return. First it has to have direct sunlight (thin turf is enough sunlight) AND if it gets water on a daily basis for several days. If you can grow a dense turf you should never see crabgrass. The second requirement is nearly continual soil surface moisture. If you can prevent yourself from watering more than once every 2-3 WEEKS in the spring and prevent Mother Nature from doing the same, then you should not see crabgrass.

So the question to ask is why was your turf thin enough to allow the crabgrass to get in? The answer could be that you have a fescue lawn instead of KBG. The way to make it a bluegrass lawn is to seed in KBG now and let the fescue die out over time. A healthy bluegrass lawn should keep crabgrass out.

If you want to fertilize I'm always going to suggest organic. Why? Too many reasons to enumerate, but for you the answer is that there is no guess work as to when and with what. Organic fertilizer can be put down any day of the year with no fear of hurting anything. You can apply at double the recommended rate with no fear of hurting anything. I would not do that, but at least the grass won't burn up. My favorite organic fertilizer is ordinary corn meal, but I like to apply alfalfa pellets at least once a year, too. The application rate for most organic fertilizers is 15-20 pounds per 1,000 square feet. If you buy it at the feed store the cost will be about $4 per 1,000 square feet which is competitive with chemical type fertilizers.

Here is a picture of an organically fertilized KBG lawn that is watered once per week in the hottest heat of summer compared to other KBG lawns that may or may not use organics but they are watered daily.

If dormant seeding works in your area (check with the local extension service), that is a good way to seed if you cannot water. The crabgrass will die after frost. You can mow it low, bagging clippings, to prepare for seed (dethatching not necessary). Get a soil test to see what nutrients it needs. If you want Morpheus here to interpret it, he prefers Logan Labs. If dormant seeding isn't advised, mid to late August is the time to plant KBG. It is slow to germinate (2-3 weeks or longer) and it's best to kill everything in July and fallow before planting. Rye is quick to germinate, fescue takes 1-2 weeks. Your local extension service could also advise on what kind of grass does well for your location. KBG generally is considered a high maintenance grass (needs more fertilizer, harder to establish). Late summer/early fall is the best time to plant cool season grass but it must be watered lightly several times a day until it germinates. Get your watering system in place before you plant anything (dormant seeding is an exception).